California has one of the world’s most sophisticated and ambitious cap-and-trade programs, which are designed to provide financial incentives to big polluters, such as electricity providers and oil refineries, to lower their greenhouse gas emissions.

The complex program, which began only in 2013, is a signature component of California’s plan to cut emissions in the midst of a controversial makeover by state policymakers, after they passed a landmark bill last year that created one of the world’s most aggressive climate change goals: to lower carbon emissions to 40% below the 1990 levels by 2030.

Fierce debates over how to achieve the new, ambitious goals began before President Trump’s decision earlier this month to withdraw the US from the Paris agreement. That decision will likely put a greater spotlight on how California – considered a leader in fighting climate change – will redesign its cap-and-trade program, which many say needs better market mechanisms and metrics to measure its successes and failures.

“It’s important to have the right architecture in place to make cap-and-trade succeed, and have it as a model for folks,” explains Senator Bob Wieckowski, a Democrat from Fremont and chair of the Senate environmental quality committee. Wieckowski, a bankruptcy attorney, is co-sponsoring a bill, SB 775, which seeks to set new parameters for the cap-and-trade program after 2020.